Real-time monitoring of MOVPE device growth by reflectance anisotropy spectroscopy and related optical techniques

Reflectance anisotropy spectroscopy (RAS/RDS) so far has been mostly used f or basic growth studies in both molecular beam epitaxy (MBE) and metal-orga nic vapor-phase epitaxy (MOVPE). Due to its sensitivity to the uppermost at omic monolayers, RAS became a very versatile tool for investigating surface stoichiometry, surface reconstruction and surface morphology especially un der gas-phase conditions. Meanwhile, however, the performance and adaptabil ity of RAS to standard MOVPE systems has been enhanced significantly and RA S sensors now can also be used for MOVPE device growth monitoring and contr ol. Therefore, after a brief introduction to the basic surface physics and surface chemistry causing the optical signatures, this paper concentrates o n device related applications. Examples will be given concerning the optica l response to both n-type and p-type GaAs doping levels and the real-time m easurement of ternary compound composition for reaching lattice matched gro wth. The optical surface response during the growth of a complete GaAs/InGa P heterojunction bipolar transistor is visualized. The result indicates on a monolayer level either consistency or deviation from the intended growth process. (C) 1998 Elsevier Science B.V. All rights reserved.